1. Field of the Invention
The present invention relates to an improvement of an intake apparatus for an internal combustion engine, and in particular of an intake apparatus provided with both an intake manifold and an intake collector.
2. Description of the Prior Art
In general, there is well known an intake apparatus for internal combustion engines for automotive vehicles provided with both an intake collector for collecting intake air via a throttle valve disposed on the downstream side of an intake passage and an intake manifold for supplying intake air uniformly distributed from the intake collector into each cylinder formed in an engine body, as disclosed in Japanese Published Unexamined (Kokai) Patent Appli. No. 63-68764.
This prior-art intake apparatus will be explained with reference to FIG. 1. An intake manifold 3 is fixed to a side surface of a cylinder head 2 of an engine 1 via a mounting flange 3a of the intake manifold 3 with bolts. Further, an intake collector 4 extending in the engine transversal direction is connected to and supported by an upwardly-curved free end 3b of the intake manifold 3. Further, a throttle body 6 accommodating twin throttle valves 5 therewithin is connected to a side portion of the intake collector 4 in such a way that a joint surface between the intake collector 4 and the throttle body 6 is declined at an inclination angle with respect to the cylinder axis. This is because the vibration of the throttle body 6 in the engine transversal direction caused when the engine 1 is running can be well suppressed by the intake collector 4.
In the prior-art intake apparatus, however, although it is possible to obtain a vibration suppressing effect to some extent in dependence upon a specific mounting structure between the intake collector 4 and the throttle body 6, since the intake collector 4 itself is connected to and supported by only the intake manifold 3, the supporting rigidity is not sufficient and therefore a large vibration is inevitably produced at both the intake collector 4 and the throttle body 6, when the engine is running.
In addition, since the intake collector 4 is connected to the upper surface of the free end 3b of the intake manifold 3, when the cylinder head 2 or fuel injection valves 7 disposed inside the intake manifold 3 are required to be removed from the engine 1 during maintenance or repair of the engine 1 or fuel injection valves 7, for instance, the intake collector 4, the throttle body 6, an intake duct connected to the throttle body 6 must be all disassembled and removed from the engine, thus resulting in an extremely troublesome maintenance and inspection work and therefore a low workability.
Further, after having been reassembled, since a number of check points such as bolt fastening, etc. are required, there exists another problem in that the working reliability is subjected to the influence of repairman's skillfulness.